Making the grade?

Sanitation officials in New York and Denver evaluate the costs of transitioning their refuse fleets from diesel to alternative fuels.

Written by Sean Kilcarr

1st September 2010

Fleet managers are anxious to see if alternative-fueled trucks’ higher sticker prices, increased vehicle weight, new maintenance processes and other issues can be offset over the long-term by the reduced diesel fuel consumption and wear-and-tear on components and systems. Few public works departments have greater demand on trucks than solid waste collection, and two large cities — New York and Denver — have been in the forefront of testing the vehicles’ performance.

New York City’s Department of Sanitation (DSNY) has had 10 Crane Carrier Corp. LET2 low-entry refuse trucks powered by compressed natural gas (CNG) on the road since early 2009, and the department deployed another 10 units earlier this year. “The CNG trucks are slightly slower off the line in comparison with our diesel-powered units, but other than that there’s no difference in performance,” says Spiro Kattan, supervisor of mechanics with DSNY’s Clean Fuels and Technologies Division.

Still, Kattan says it will be some time before a firm verdict on alternatively fueled vehicles is reached. Tracking their performance in various types of weather needs to be further explored, he says. “As we operate in the northeastern U.S., we’re subject to big swings in temperature,” Kattan points out. “Though we had a lot of snow during this past winter, we didn’t have really long stretches of freezing temperatures. We need that ‘real world’ cold for truly testing our CNG trucks.”

Plowing snow is another operation for which more data is needed. “We equip all of our refuse trucks with snow plows to aid in snow-removal operations,” Kattan says. “So, we need to track the snow plow performance of our CNG-powered trucks over several snowstorms to get an accurate gauge of their capability. You can’t depend on just one or two snowfalls to give us the data we need. The more information we gather, the better.”

The same issues apply to the other alternatively fueled vehicles DSNY is testing: a Mack TerraPro low-entry, parallel hybrid diesel-electric truck; a Crane Carrier low-entry diesel hybrid equipped with a Bosch Rexroth Hydrostatic Regenerative Braking (HRB) parallel hydraulic system; and a Crane Carrier low-entry model equipped with an ISE diesel-electric hybrid series drive system. Each is being evaluated for fuel savings, emission reductions, component life, maintenance costs, reliability and uptime, as well as any operational issues observed by drivers. “We need time to get to a point where we have enough solid data to draw true comparisons between these technologies and traditional diesel-only trucks,” Kattan says.

Regional differences

Of course, where refuse trucks operate affects the long-term calculations of using alternative fuels. DSNY notes that its Mack and Crane Carrier trucks — each of which has a gross vehicle weight of 72,000 pounds — are deployed in regular residential trash collection service across the multitude of driving patterns and duty cycles.

Now, contemplate similar tests being undertaken by Denver — a place that adds factors that New York does not experience, such as more frequent and heavier snowfalls, longer stretches of extremely cold temperatures, and high altitude. Nancy Kuhn, fleet administrator for Denver’s fleet management division, says B20 biodiesel, which consists of 20 percent soybean-based biodiesel and 80 percent regular diesel, has been fueling all of the city’s diesel-powered vehicles and equipment (about 850 units), including its fleet of 120 trash and recycling trucks, since 2004 with no problems.

Denver tapped biodiesel for a simple reason: it was the easiest alternative fuel to implement, with no modifications required to its vehicles or maintenance facilities and a $1 per gallon biodiesel tax credit, making the transition affordable. “We’ve gone to B10 on occasion to remain within budget,” she says. “But in 2010, grant money offset the incremental costs of using this alternative fuel.”

Hybrids are Denver’s next area of research, with 142 hybrids operating in its fleet, among them a heavy-duty Peterbilt hybrid trash truck equipped with Eaton Corp.’s Hydraulic Launch Assist (HLA) technology. “Our hybrid-hydraulic trash truck is considered a test unit, allowing the manufacturer to gather fuel data and monitor performance and brake wear in Denver’s high-altitude, cold-climate conditions,” Kuhn says.

He says the units are getting 25 percent better fuel economy than the city’s non-hybrid units. Kuhn adds that the city is pinning multiple hopes on its heavy-duty hydraulic-hybrid refuse truck, such as reduced exhaust emissions, decreased petroleum consumption, and better resale value — especially if fuel prices spike again.

Save me the money

One of the major keys to the long-term viability of any alternatively fueled vehicle boils down to two words: cost savings. Recent research by the Phoenix-based WIH Resource Group, a waste industry consulting firm, determined that alternative fuels, in particular natural gas, can save money, but primarily over the long haul. The company’s research indicates that an average price of natural gas, compared with traditional diesel, is about $1 less per diesel gallon equivalent (DGE) when refuse truck operators are able to get fixed-price, multi-year natural gas fueling contracts from suppliers. Without such contracts, natural gas typically runs about 50 cents per DGE cheaper than diesel, the group notes.

WIH says using natural gas as a vehicle fuel also helps reduce U.S. dependence on foreign crude oil. For example, in 2005, 64 percent of the crude oil used in the United States was imported from foreign sources other than Canada. By comparison, an estimated 97 percent of the natural gas used in the United States that same year came from domestic or Canadian sources, making natural gas less vulnerable to foreign supply disruption and price volatility. The CNG market also tends to be more stable than the gasoline market, typically costing anywhere from 15 percent to 40 percent less than gasoline or diesel, WIH says.

However, CNG-powered trucks require more frequent refueling because the gas contains only about one-quarter of the energy by volume of diesel. Also, CNG vehicles cost $1,500 to $3,500 more per year than their diesel-powered counterparts, primarily because of the higher cost of maintaining the CNG fuel-storage cylinders on the trucks. Yet, once new natural gas trucks are in service, WIH found, their operators can save money. Not only has the price of natural gas been trending lower than diesel fuel, but an excise tax credit available under the federal 2005 Energy Policy Act made CNG an even better bargain in some cases. For example, WIH estimates one city’s 20 CNG trash trucks could produce fuel savings of more than $157,894 per year over diesel fuel, in no small part because of those tax credits.

Potential savings like that are one of several reasons why many refuse fleets — in the public and private sectors alike — continue to experiment with a wide variety of alternative fuels, even though a complete operational picture of their benefits and drawbacks has yet to be painted.

This article was extracted from a Waste Age August 2010 feature and written by Sean Kilcarr, senior editor of Fleet Owner. Waste Age and Fleet Owner are sister publications of American City & County.

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